U.S. patent application number 11/097475 was filed with the patent office on 2006-10-05 for stacked-tube heat exchanger.
Invention is credited to Michael A. Martin, Alan K. Wu.
Application Number | 20060219394 11/097475 |
Document ID | / |
Family ID | 37068933 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060219394 |
Kind Code |
A1 |
Martin; Michael A. ; et
al. |
October 5, 2006 |
Stacked-tube heat exchanger
Abstract
A headerless heat exchanger has a core comprised of a stack of
flat tubes of rectangular cross section through which a first heat
exchange fluid passes. The tubes are expanded in height at their
end portions to provide spaces between adjacent plate pairs for
passage of a second heat exchange fluid between the tubes. The
sides of the tubes are coplanar, at least in the end portions of
the tubes, to provide flat surfaces along which the core is sealed
to side plates of the heat exchanger, for example by brazing or
welding. The side plates may be separately formed or may comprise
part of a continuous housing. The tubes are preferably formed from
plate pairs having nesting side walls.
Inventors: |
Martin; Michael A.;
(Hamilton, CA) ; Wu; Alan K.; (Kitchener,
CA) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
39577 WOODWARD AVENUE
SUITE 300
BLOOMFIELD HILLS
MI
48304-5086
US
|
Family ID: |
37068933 |
Appl. No.: |
11/097475 |
Filed: |
April 1, 2005 |
Current U.S.
Class: |
165/157 ;
165/166 |
Current CPC
Class: |
F28D 21/0003 20130101;
F28F 3/025 20130101; F28F 2240/00 20130101; F28F 9/0221 20130101;
F28F 2235/00 20130101; F28D 9/0043 20130101; F28F 2009/029
20130101; F28F 2001/027 20130101 |
Class at
Publication: |
165/157 ;
165/166 |
International
Class: |
F28D 7/10 20060101
F28D007/10; F28F 3/00 20060101 F28F003/00 |
Claims
1. A heat exchanger for heat transfer between a first fluid and a
second fluid, the heat exchanger comprising: (a) a core comprising
a stack of tubes, each of the tubes having a top wall, a bottom
wall, side walls connecting the top and bottom walls, a hollow
interior enclosed by the top, bottom and side walls, and inlet and
outlet openings for the first fluid; wherein each of the tubes has
a pair of end portions spaced apart along a longitudinal axis and a
central portion located between the end portions, the end portions
of adjacent tubes in the core being sealed to one another along
their top and bottom walls, wherein the end portions are greater in
height than the central portions of the tubes such that the central
portions of adjacent tubes in the core are spaced from one another;
(b) a plurality of first fluid flow passages, each of which
comprises the hollow interior of one of the tubes and extends
longitudinally from the first fluid inlet opening to the first
fluid outlet opening; (c) a plurality of second fluid flow
passages, each of which comprises the space between the central
portions of an adjacent pair of said tubes, each of the second
fluid flow passages having a pair of longitudinally-spaced ends and
a pair of transversely spaced sides, each of the second fluid flow
passages being sealed along its ends by the end portions of said
adjacent pair of tubes; and (d) a pair of side plates covering the
transversely spaced sides of the second fluid flow passages, the
side plates engaging the side walls of the tubes in the core and
being sealed to the tube side walls in the end portions of the
tubes, wherein a second fluid inlet manifold is provided in one of
the side plates and a second fluid outlet manifold is provided in
one of the side plates, each of the manifolds communicating with
each of the second fluid flow passages.
2. The heat exchanger according to claim 1, further comprising a
top plate extending between the side plates and sealed to the top
wall of an uppermost tube in the core, in the end portions thereof,
the top plate being spaced from the central portion of the
uppermost tube so as to form an uppermost flow passage for the
second fluid, the uppermost flow passage being in communication
with the second fluid inlet and outlet manifolds.
3. The heat exchanger according to claim 2, further comprising a
bottom plate extending between the side plates and sealed to the
end portions in the bottom wall of a lowermost tube in the core,
the bottom plate being spaced from the central portion in the
bottom wall of the lowermost tube so as to form a lowermost flow
passage for the second fluid, the lowermost flow passage being in
communication with the inlet and outlet manifolds.
4. The heat exchanger according to claim 3, wherein the side
plates, top plate and bottom plate comprise a continuous housing
covering the core along its top, bottom and side surfaces.
5. The heat exchanger according to claim 4, wherein the housing is
formed from either a cylindrical tube or from a sheet of metal.
6. The heat exchanger according to claim 1, wherein each of the
side plates has a substantially flat side wall, each of the
manifolds comprises an upstanding portion of the side plate in
which the side wall is spaced from the side walls of the tubes.
7. The heat exchanger according to claim 1, wherein both the inlet
and outlet manifolds are formed in one of the side plates.
8. The heat exchanger according to claim 1, wherein the inlet
manifold is formed in a first one of the side plates and the outlet
manifold is formed in a second one of the side plates.
9. The heat exchanger according to claim 1, wherein the end
portions of the tubes comprise upstanding shoulders on both the top
and bottom walls and substantially flat end surfaces extending
between the shoulders and the ends of the tubes, and wherein
adjacent pairs of tubes engage one another and are sealed together
along their substantially flat end surfaces.
10. The heat exchanger according to claim 1, wherein each of the
tubes has a rectangular transverse cross-sectional shape, wherein
the top and bottom walls are substantially flat and parallel to one
another, and wherein each of the tubes has a pair of side walls
which are substantially flat and parallel to one another.
11. The heat exchanger according to claim 10, wherein the side
walls of the tubes along each side of the core are substantially
flat and coplanar and are in engagement with one of the side
plates.
12. The heat exchanger according to claim 11, wherein the tubes are
of constant width.
13. The heat exchanger according to claim 1, wherein the tubes are
open-ended and the first fluid inlet and outlet openings are formed
at the open ends of the tubes, and wherein the heat exchanger
further comprises inlet and outlet fittings located at opposite
ends of the core and communicating with the open ends of the
tubes.
14. The heat exchanger according to claim 13, wherein each of the
inlet and outlet fittings comprises a longitudinal flange which
overlaps with and is sealed to the end portions of the tubes.
15. The heat exchanger according to claim 14, wherein a
longitudinally-extending gap is provided between the longitudinal
flange of each of the end fittings and the side plates.
16. The heat exchanger according to claim 15, further comprising:
(a) a top plate extending between the side plates and sealed to the
top wall of an uppermost tube in the core, in the end portions
thereof, the top plate being spaced from the central portion of the
uppermost tube so as to form an uppermost flow passage for the
second fluid, the uppermost flow passage being in communication
with the second fluid inlet and outlet manifolds; and (b) a bottom
plate extending between the side plates and sealed to the end
portions in the bottom wall of a lowermost tube in the core, the
bottom plate being spaced from the central portion in the bottom
wall of the lowermost tube so as to form a lowermost flow passage
for the second fluid, the lowermost flow passage being in
communication with the inlet and outlet manifolds; wherein the
longitudinal flange of each of the end fittings is spaced
longitudinally from the top and bottom plates.
17. The heat exchanger according to claim 1, wherein at least one
of the first fluid inlet opening and the first fluid outlet opening
of each tube comprises a pair of aligned apertures in one of the
end portions of said tube, one of the apertures being formed in the
top wall of the tube and the other aperture being formed in the
bottom wall of the tube, and wherein the apertures in adjacent
tubes align with one another to form an inlet and/or outlet
manifold of the heat exchanger.
18. The heat exchanger according to claim 1, wherein the central
portions of the tubes are provided with upstanding protrusions in
one or both of their top and bottom walls, the protrusions each
having an upper surface which engages the top or bottom wall of the
same tube or an adjacent tube.
19. The heat exchanger according to claim 18, wherein the
protrusions of adjacent tubes engage each other.
20. The heat exchanger according to claim 1, wherein
turbulence-enhancing inserts are provided in one or more of the
first fluid flow passages, each of the turbulence-enhancing inserts
having a height which is substantially the same as a height of the
first fluid flow passage in which it is received, and wherein each
of the turbulence-enhancing inserts has an upper surface engaging
the top wall of the tube and a lower surface engaging the bottom
wall of the tube.
21. The heat exchanger according to claim 1, wherein each of the
tubes comprises a pair of plates, each of the plates having a pair
of longitudinally-extending side portions, and wherein the plates
are sealed together along their side portions and are spaced from
one another between the side portions to form one of said first
fluid flow passages.
22. The heat exchanger according to claim 21, wherein each of the
plates is U-shaped, having a generally flat middle portion between
the longitudinally-extending side portions, and wherein the side
portions of the plate are angled relative to the middle
portion.
23. The heat exchanger according to claim 22, wherein the side
portions of the plates are substantially parallel to one another
and are angled by about 90 degrees relative to the middle
portion.
24. The heat exchanger according to claim 22, wherein the side
portions of each pair of plates nest with one another.
25. The heat exchanger according to claim 24, wherein each of said
plate pairs comprises a first plate and a second plate, the side
portions of the first plate nesting inside the side portions of the
second plate and wherein the side portions of the second plate have
a greater height than the side portions of the first plate.
26. The heat exchanger according to claim 25, wherein the side
portions of the second plate have a height substantially the same
as a height of the first fluid flow passage throughout their entire
length.
27. The heat exchanger according to claim 24, wherein each of said
plate pairs comprises a first plate and an identical second
plate.
28. The heat exchanger according to claim 1, wherein each of the
side plates is U-shaped, comprising a side wall covering one side
of the core and a pair of longitudinally-extending flanges angled
relative to the side wall, one of the flanges sealingly engaging
the top wall of the uppermost tube in the core and the other of the
flanges sealingly engaging the bottom wall of the lowermost tube in
the core.
29. The heat exchanger according to claim 1, wherein gaps are
formed between the side walls of adjacent tubes in the core, in the
end portions thereof, and wherein the side plates have end portions
which are provided with a series of spaced ribs which extend into
and at least partially fill said gaps.
30. A method for manufacturing a heat exchanger comprising a core
comprised of a stack of open-ended tubes, each of the tubes having
a top wall, a bottom wall, side walls connecting the top and bottom
walls, a hollow interior enclosed by the top, bottom and side
walls, and inlet and outlet openings for the first fluid, wherein
each of the tubes has a pair of end portions spaced apart along a
longitudinal axis and a central portion located between the end
portions, the end portions of adjacent tubes in the core being
sealed to one another along their top and bottom walls, wherein the
end portions are greater in height than the central portions of the
tubes such that the central portions of adjacent tubes in the core
are spaced from one another; a plurality of first fluid flow
passages, each of which comprises the hollow interior of one of the
tubes and extends longitudinally from one open end of the tube to
the other open end; a plurality of second fluid flow passages, each
of which comprises the space between the central portions of an
adjacent pair of said tubes, each of the second fluid flow passages
having a pair of longitudinally-spaced ends and a pair of
transversely spaced sides, each of the second fluid flow passages
being sealed along its ends by the end portions of said adjacent
pair of tubes; and a pair of U-shaped side plates, each of which
has a side wall covering one side of the core and a pair of
longitudinally-extending edges which are sealed to an uppermost
tube in the core and a lowermost tube in the core, respectively,
the side plates having inlet and outlet openings for the second
fluid; the method comprising: (a) stacking said tubes to form said
core; (b) attaching said U-shaped side plates to opposite sides of
the core with one of the longitudinally-extending edges of each
side plate engaging the top wall of the uppermost tube in the core
and the other edge of each side plate engaging the bottom wall of
the lowermost tube in the core, wherein the edges of the side
plates frictionally engage the uppermost and lowermost tubes to
retain the tubes in position in said core; and (c) heating the core
with the attached side plates for a time and at a temperature
sufficient to seal the end portions of adjacent tubes together, to
seal the longitudinally-extending edges of the side plates to the
uppermost and lowermost tubes in the core, and to seal the side
plates to the tube side walls in the end portions of the tubes.
31. The method of claim 30, further comprising the step of
attaching inlet and outlet fittings to opposite ends of the core,
the fittings having longitudinally-extending flanges which fit
over, and frictionally engage, the end portions of the uppermost
and lowermost tubes along their respective top and bottom walls,
followed by joining the end fittings to the core.
Description
FIELD OF THE INVENTION
[0001] The invention relates to heat exchangers, and particularly
to heat exchangers including a stack of spaced-apart tubes and/or
plate pairs which define flow passages for first and second
fluids.
BACKGROUND OF THE INVENTION
[0002] Heat exchangers are commonly constructed from stacks or
bundles of spaced-apart flat tubes, in which the interiors of the
tubes define flow passages for a first fluid and in which spaces
between adjacent tubes define flow passages for a second fluid. The
flat tubes may comprise pairs of flat plates joined together at
their margins.
[0003] The ends of the tubes in the stack or bundle are usually
retained by a perforated header or tube sheet and the spaces
between the plates may be at least partially enclosed by a housing.
Examples of exhaust gas heat exchangers of this type are shown in
U.S. Pat. No. 6,293,337 (Strahle et al.) and in U.S. Pat. No.
6,269,870 (Banzhaf et al.).
[0004] It is also known to construct heat exchangers comprising
bundles of spaced-apart flat tubes in which the need for a
perforated header is eliminated. An example of a heat exchanger
having this type of construction is described in U.S. Pat. No.
6,321,835 (Damsohn et al.). In this patent, the ends of the heat
exchanger tubes are expanded in width and height relative to the
central portions of the tubes. The tube ends are sealed directly to
one another and to the housing, thereby eliminating the need for a
perforated header.
[0005] There remains a need to provide stacked-tube heat exchangers
of simplified, reliable construction and to improve and simplify
processes for manufacturing such heat exchangers.
SUMMARY OF THE INVENTION
[0006] In one aspect, the present invention provides a heat
exchanger for heat transfer between a first fluid and a second
fluid. The heat exchanger comprises: (a) a core comprising a stack
of tubes, each of the tubes having a top wall, a bottom wall, side
walls connecting the top and bottom walls, a hollow interior
enclosed by the top, bottom and side walls, and inlet and outlet
openings for the first fluid, wherein each of the tubes has a pair
of end portions spaced apart along a longitudinal axis and a
central portion located between the end portions, the end portions
of adjacent tubes in the stack being sealed to one another along
their top and bottom walls, wherein the end portions are greater in
height than the central portions of the tubes such that the central
portions of adjacent tubes in the stack are spaced from one
another; (b) a plurality of first fluid flow passages, each of
which comprises the hollow interior of one of the tubes and extends
longitudinally from the first fluid inlet opening to the first
fluid outlet opening; (c) a plurality of second fluid flow
passages, each of which comprises the space between the central
portions of an adjacent pair of the tubes, each of the second fluid
flow passages having a pair of longitudinally-spaced ends and a
pair of transversely spaced sides, each of the second fluid flow
passages being sealed along its ends by the end portions of the
adjacent pair of tubes; and (d) a pair of side plates covering the
transversely spaced sides of the second fluid flow passages, the
side plates engaging the side walls of the tubes in the stack and
being sealed to the tube side walls in the end portions of the
tubes, wherein an inlet manifold is provided in one of the side
plates and an outlet manifold is provided in one of the side
plates, each of the manifolds communicating with each of the second
fluid flow passages.
[0007] In another aspect, the present invention provides a method
for manufacturing a heat exchanger according to the invention. The
method comprises: (a) stacking the tubes to form the core; (b)
attaching the U-shaped side plates to opposite sides of the core
with one of the longitudinally-extending edges of each side plate
engaging the top wall of the uppermost tube in the core and the
other edge of each side plate engaging the bottom wall of the
lowermost tube in the core, wherein the edges of the side plates
frictionally engage the uppermost and lowermost tubes to retain the
tubes in position in the core; and (c) heating the core with the
attached side plates for a time and at a temperature sufficient to
seal the end portions of adjacent tubes together, to seal the
longitudinally-extending edges of the side plates to the uppermost
and lowermost tubes in the core, and to seal the side plates to the
tube side walls in the end portions of the tubes and to tubes to
one another and to the side plates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention will now be described, by way of example only,
with reference to the accompanying drawings in which:
[0009] FIG. 1 is a perspective view of a heat exchanger according
to a first preferred embodiment of the invention;
[0010] FIG. 2 is an exploded perspective view of the heat exchanger
of FIG. 1;
[0011] FIG. 3 is a cross section along the line 3-3' of FIG. 1;
[0012] FIG. 4A is a close-up of area B of FIG. 3;
[0013] FIG. 4B is a close-up of area B of FIG. 3 according to a
variant of the first preferred embodiment;
[0014] FIG. 4C is a close-up of area B of FIG. 3 according to
another variant of the first preferred embodiment;
[0015] FIG. 5 is a front elevation view of the heat exchanger of
FIG. 1, with the end caps removed;
[0016] FIG. 6 is a front elevation view of one of the tubes making
up the heat exchanger of FIG. 1;
[0017] FIG. 7 is a front elevation view of an alternate tube
construction for use in a heat exchanger according to the
invention;
[0018] FIG. 8 is a perspective view of a heat exchanger according
to a second preferred embodiment of the invention;
[0019] FIG. 9 is an exploded perspective view of the heat exchanger
of FIG. 8;
[0020] FIG. 10 is a perspective view of a heat exchanger according
to a third preferred embodiment of the invention;
[0021] FIG. 11 is an exploded perspective view of the heat
exchanger of FIG. 10;
[0022] FIG. 12 is an exploded perspective view of a heat exchanger
according to a fourth preferred embodiment of the invention;
[0023] FIG. 13 is a close-up of area C of FIG. 5;
[0024] FIG. 14 is a close-up of a portion of a heat exchanger
according to a fifth preferred embodiment of the invention;
[0025] FIG. 15 is a perspective view of one plate pair of a heat
exchanger according to a sixth preferred embodiment of the
invention;
[0026] FIG. 16 is an exploded perspective view of a heat exchanger
according to a seventh preferred embodiment of the invention;
and
[0027] FIG. 17 is a perspective view of the heat exchanger of FIG.
16.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] Heat exchangers according to the invention are suited for
use as exhaust gas coolers for vehicular applications in which hot
exhaust gases are cooled by a liquid coolant, for example to cool
or prevent overheating of the catalyst in a catalytic converter
and/or to provide supplementary cabin heating. It will, however, be
appreciated that the heat exchangers described herein can be
applied to a number of different uses other than the cooling of
exhaust gases. For example, heat exchangers according to the
invention can be used for reformer-based fuel processors.
[0029] A first preferred heat exchanger 10 is illustrated in FIGS.
1 to 5. Heat exchanger 10 comprises a core 11 (FIGS. 2, 3 and 5)
comprising a stack of open-ended tubes 12, each of which has a top
wall 14, an opposed bottom wall 16 and a pair of opposed side walls
18, 20. The tubes 12 each have a pair of end portions 22, 24 spaced
apart along longitudinal axis A and a central portion 26 located
between the end portions 22, 24. The central portions 26 of
adjacent tubes 12 are spaced apart while the end portions 22, 24 of
adjacent tubes 12 are sealed to one another along their top and
bottom walls 14, 16.
[0030] In heat exchanger 10, the tubes 12 have a rectangular
cross-section when viewed in a transverse plane, with the top and
bottom walls 14,16 being substantially flat and parallel to one
another and with the side walls 18,20 being substantially flat and
parallel to one another. It will, however, be appreciated that the
tubes 12 may be of other suitable shapes, preferably having
substantially flat top and bottom walls 14,16. For example, the
cross sections of tubes 12 may be shaped as elongate hexagons or as
elongate ovals in which the side walls 18, 20 are multi-faceted or
rounded. However, it is preferred that the tubes 12 have an
elongate rectangular cross sectional shape, as shown in the
drawings, so as to simplify the shapes of other components of the
heat exchanger, which are described below.
[0031] The tubes 12 in heat exchanger 10 are of constant width and
have end portions 22, 24 which are expanded in the vertical
direction so that the end portions 22, 24 have a height which is
greater than a height of the central portions 26 of tubes 12. This
permits the central portions 26 of the tubes 12 to be spaced apart
while the end portions 22, 24 of adjacent tubes 12 may be sealed
directly to one another without the need for a perforated header or
tube sheet. It will be appreciated that the width of the tubes is
not necessarily constant throughout their length.
[0032] Heat exchanger 10 includes fluid flow passages for heat
exchange between a first fluid and a second fluid, which may be
either liquid or gaseous. A plurality of first fluid flow passages
30 is defined by the hollow interiors of tubes 12. Each of the
first fluid flow passages 30 extends longitudinally from one open
end 34 to another open end 36 of a tube 12. Where heat exchanger 10
comprises an exhaust gas cooler, the first fluid is preferably a
hot engine exhaust gas.
[0033] A plurality of second fluid flow passages 38 is defined by
the spaces between the central portions 26 of adjacent tubes 12.
Each of the second fluid flow passages 38 has a pair of
longitudinally-spaced ends 40 and a pair of transversely spaced
sides 42. As shown in FIG. 3, the second fluid flow passages 38 are
sealed along their ends 40 by the sealed end portions 22, 24 of the
adjacent tubes 12 between which they are formed.
[0034] The heat exchanger 10 further comprises a housing 44 which
covers the top, bottom and sides of the core 11. The housing 44 is
open-ended, has a rectangular transverse cross section and
comprises a pair of side plates 46, 48 and a pair of end plates 50,
52. As shown in the drawings, the housing 44 may comprise a
pre-formed rectangular casing made from a drawn pipe which is
formed into a rectangular shape, or from sheet metal which is
stamped or folded into a rectangular shape and joined along a seam
by welding or brazing. Although the housing 44 is shown in the
drawings as having a rectangular shape, it will be appreciated that
it may have any other suitable shape, depending on the shape of the
core 11.
[0035] The side plates 46, 48 of housing 44 substantially enclose
the sides 42 of the second fluid flow passages 38 and may
preferably engage the side walls 18, 20 of the tubes 12, thereby
substantially preventing bypass flow between the tube side walls
18, 20 and the side plates 46, 48. In the preferred heat exchanger
10, the side plate 46 is provided with an inlet opening 54 which is
formed in a raised inlet manifold 56. The manifold 56 comprises a
raised portion of side plate 46 which extends throughout
substantially the entire height of the side plate 46 so as to
permit flow communication between the inlet opening 54 and each of
the second fluid flow passages 38. The other side plate 48 is
provided with an outlet opening 58 and an outlet manifold 60
substantially identical to the inlet opening and manifold 54, 56
described above. Although heat exchanger 10 has inlet and outlet
openings 54,58 and the associated manifolds 56, 60 formed in
opposite side plates 46,48 of housing 44, they may instead be
provided in the same side plate 46 or 48. Furthermore, where the
openings 54, 58 are provided in opposite side plates 46, 48, it
will be appreciated that they are not necessarily offset from one
another. Rather, the openings 54, 58 may be located directly
opposite to one another, as will be discussed below in more
detail.
[0036] The end plates 50, 52 extend between and are connected to
the side plates 46, 48. As shown in FIG. 3, an additional second
fluid flow passage 62 is formed between the top end plate 50 and
the top wall 14 of the uppermost tube 12 of core 11, and an
additional fluid flow passage 64 is formed between the bottom end
plate 52 and the bottom wall 16 of the lowermost tube 12 of core
11. These passages 62, 64 are also in communication with the inlet
and outlet openings 54, 58 through manifolds 56, 60.
[0037] Referring now to FIGS. 3 and 4, it will be seen that the
longitudinally-spaced ends of housing 44 are sealed to the end
portions of the tubes 12 in the core 11, thereby sealing the ends
of the second fluid flow passages 38, 62, 64. Specifically, as
shown in FIG. 3, it will be seen that the ends of top end plate 50
overlap with and sealingly engage the end portions 22, 24 of
uppermost tube 12 and the ends of bottom end plate 52 overlap with
and sealingly engage the end portions 22, 24 of the lowermost tube
12. Similarly, as shown in FIG. 5, the side plates 46, 48 of
housing 44 sealingly engage the side walls 18, 20 of tubes 12, at
least along their end portions 22, 24, throughout the height of the
core 11.
[0038] The heat exchanger 10 preferably also comprises a pair of
end fittings 68 which, in the first preferred embodiment, are
identical to each other. Fittings 68 form an inlet and outlet for
the first fluid and are in flow communication with the first fluid
flow passages 30 at the ends 34, 36 of tubes 12. Each of the end
fittings 68 has a longitudinally-extending flange 70 which is of
substantially square or rectangular shape. The flange 70 fits over
and is sealed to the end portions 22, 24 of the stacked tubes 12
or, as described below in greater detail, may overlap the ends of
housing 44.
[0039] There are various methods by which the heat exchanger 10 may
be assembled. According to one method, the tubes 12 comprising the
core 11 are brazed together and the core 11 is then slid as a unit
into a pre-formed housing 44, with the walls 46, 48, 50 and 52
overlapping the ends 22, 24 of the tubes 12. The end fittings 68
are then slid over the ends of the core 11, with a small gap 72
being provided between the flange 70 and the housing 44, as shown
in the close-up of FIG. 4A. The provision of gap 72 is advantageous
where the fittings 68, housing 44 and core 11 are simultaneously
brazed or welded together. The gap 72 is filled by a filler metal
during brazing or welding, and the filler metal is drawn into the
gaps between the tubes 12, the housing 44 and the end fittings 68
by capillary flow, thereby ensuring a leak-proof seal.
Alternatively, the flanges 70 of fittings 68 may overlap the ends
of the housing 44, as shown in the close-up of FIG. 4B.
[0040] In other assembly methods, the housing 44 may be formed from
a sheet of metal which is wrapped around the core 11, held in
tension and then fastened together by welding, mechanical fasteners
or staking. In this type of assembly method, the end fittings 68
can be applied to the core either before or after the housing 44.
For example, the end fittings 68 may first be applied over the ends
of an unbrazed core 11, whereby frictional engagement between the
flanges 70 of the end fittings 68 and the tubes 12 is sufficient to
hold the core together during brazing. This reduces or eliminates
the need for additional fixturing means to keep the tubes 12 from
shifting their relative positions in the tube stack prior to
brazing. Accordingly, the end fittings 68 provide "self-fixturing"
during assembly of the heat exchanger and simplify the
manufacturing process. The fittings 68 and core 11 are then brazed
together. The housing 44 is subsequently wrapped around the core 11
and may either overlap the flanges 70 of the end fittings 68, as
shown in the close-up of FIG. 4C or be spaced from the fittings as
in FIG. 4A. The housing 44 is then welded to the flanges 70 and to
the underlying tubes 12.
[0041] As shown in FIG. 3, the central portions 26 of tubes 12 are
preferably provided with upstanding protrusions 77 in one or both
of their top and bottom walls 14, 16. In all but the uppermost and
lowermost tubes 12, the upper surfaces 79 of protrusions 77 engage
the top or bottom wall 14, 16 or a protrusion 77 of an adjacent
tube 12. The protrusions 77 in the top wall 14 of the uppermost
tube 12 preferably engage the end wall 50 of housing 44 and the
protrusions 77 in the bottom wall 16 of the lowermost tube
preferably engage the end wall 52 of housing 44. It will be
appreciated that protrusions 77 assist in maintaining the spaces
between the central portions 26 of adjacent tubes 12 by providing
support between the top and bottom walls 14, 16, thereby enhancing
the strength of the heat exchanger 10.
[0042] In the first preferred embodiment, the protrusions 77 are in
the form of spaced dimples having a truncated cone shape, the upper
surfaces 79 of the protrusions being flat. Preferably, both the top
and bottom walls 14, 16 are provided with protrusions 77 arranged
in the same pattern so that the upper surfaces 79 of the
protrusions 77 of adjacent tubes 12 engage one another as shown in
FIG. 3. It will be appreciated that the tubes 12 may be provided
with protrusions 77 other than, or in addition to, dimples 77. For
example, the tubes could be provided with spaced, angled ribs
provided in their top and/or bottom walls 14, 16.
[0043] The heat exchanger 10 preferably also comprises
turbulence-enhancing inserts provided in one or more of the first
fluid flow passages 30, preferably in all the first fluid flow
passages 30. As shown in FIG. 5, the turbulence-enhancing inserts
comprise a plurality of corrugated fins 80, each of which comprises
a plurality of longitudinally-extending fin walls 82 having a
height substantially equal to the height of the first fluid flow
passages 30 in the central portions 26 of tubes 12. The fin walls
82 are connected by top and bottom walls 83, 84 which are in heat
exchange contact with the top and bottom walls 14, 16,
respectively, of tubes 12. In order to maximize contact between the
fins 80 and tubes 12, the top and bottom walls 83, 84 of fins 80
may preferably be flat, although this is not necessary.
[0044] In order to simplify the manufacturing process and reduce
cost, it is preferred that each of the tubes 12 is comprised of a
pair of plates, which in the first preferred embodiment, are
identified as upper plate 88 and lower plate 90 (FIGS. 5 and 6).
Each of the plates have a pair of longitudinally-extending side
portions along which the plates 88, 90 are sealed together. In the
first preferred embodiment, the plates 88, 90 are generally
U-shaped, with the upper plate 88 having a pair of identical side
portions 92 joined by a substantially flat middle portion 96, and
the lower plate 90 has a pair of identical side portions 94 joined
by a substantially flat middle portion 98. The angle between middle
portions 96, 98 and respective side portions 92, 94 is about 90
degrees.
[0045] In order to provide good sealing contact between the plates
88, 90, the side portions 92, 94 of the plates 88, 90 are
preferably in nested relation. This is shown in FIGS. 5 and 6, from
which it can be seen that the shorter side portions 92 of the upper
plate 88 are completely nested inside (i.e. between) the relatively
longer side portions 94 of lower plate 90, thereby providing good
contact for a braze joint between the side portions 92, 94. It can
also be seen from the end view of FIG. 5 that the side portions 94
of lower plate 90 are sufficiently long to extend up to the top
wall 14 of tube 12 in the end portions 22, 24 thereof, and
preferably into contact with the bottom wall 16 of an upwardly
adjacent tube 12. As shown in FIGS. 5 and 13, this minimizes the
size of the gaps 100 formed between the side walls 18, 20 of
adjacent tubes 12, thereby ensuring that a well sealed braze joint
will be formed between the side walls of tubes 12 and the side
plates 44.
[0046] In the tube 12 shown in FIG. 6, the corrugated fin 80 also
serves as a spacer to maintain the desired degree of nesting
between plates 88, 90 and the height of first fluid flow passages
30.
[0047] It will be appreciated that the construction of the tubes
for heat exchangers according to the invention may vary from that
shown in FIGS. 1 to 6. FIG. 7 shows an alternate construction for a
heat exchanger tube 102 which, except for the details of its
construction described below, is preferably identical to tube 12.
The tube 102 comprises a pair of identical U-shaped plates 104
having a pair of side portions 106, 108 joined by a middle portion
110. The side portions 106, 108 are of different lengths, with side
portion 106 being higher than side portion 108. When two plates 104
are brought together in nested engagement as shown in FIG. 6, the
higher side portions 106 are on the outside of the shorter side
portions 108. As in tube 12, a corrugated fin 80 is preferably
provided for turbulence and to maintain the spacing between the
plates 104.
[0048] A second preferred heat exchanger 120 according to the
invention is now described with reference to FIGS. 8 and 9. Heat
exchanger 120 includes a core 11 and end fittings 68 which are
identical to those of heat exchanger 10 described above. Heat
exchanger 120 differs from heat exchanger 10 in that it does not
include a housing 44, but rather utilizes a pair of side plates
122, 124 to seal the sides of the second fluid flow passages 38.
Side plate 122 is provided with an inlet opening 126 and an inlet
manifold 128 and side plate 124 is provided with an outlet opening
130 and an outlet manifold 132, which are preferably identical to
the inlet and outlet openings and manifolds of heat exchanger 10
described above. It will be appreciated that both the inlet and
outlet openings 126, 130 and the associated manifolds 128,132 may
instead be provided side-by-side in one of the plates 122 or 124.
Where the inlet and outlet openings 126, 130 are provided in
opposite side plates 122, 124, they are not necessarily offset from
one another, but rather may be directly opposite one another as
described below in more detail.
[0049] Each side plate 122,124 is sealed to the side walls 18, 20
of the tubes 12 along one side of the core 11, at least in the end
portions 22,24 of the tubes 12. The side plates 122,124 are
preferably U-shaped, having angled flanges which are sealed to the
central portions 26 of the uppermost and lowermost tubes 12 in the
core 11, thereby sealing the sides of the second fluid flow
passages 38. The flanges preferably terminate short of the end
portions 22, 24 of tubes 12. As shown in FIGS. 8 and 9, side plate
122 is provided with flanges 134, 136 and side plate 124 is
provided with flanges 138, 140. One flange 134 of plate 122 is
sealed to the top wall 14 of the uppermost tube 12 and, although
not visible in the drawings, the other flange 136 is sealed to the
bottom wall 16 of the lowermost tube 12. Similarly, the flanges
138,140 of the other plate 124 are sealed to the uppermost and
lowermost tubes 12, respectively.
[0050] Preferably, during assembly of the heat exchanger 10, the
angled flanges of plates 122,124 frictionally engage the uppermost
and lowermost tubes 12, thereby reducing or eliminating the need
for additional fixturing means to keep the tubes 12 from shifting
their relative positions in the core 11 prior to brazing.
Accordingly, the side plates 122,124 provide "self-fixturing"
during assembly of the heat exchanger and simplify the
manufacturing process.
[0051] FIGS. 10 and 11 illustrate a third preferred heat exchanger
150 according to the invention. Heat exchanger 150 includes a core
comprising a stack of tubes 152 which are similar to tubes 12 in
that each has a top wall 154, an opposed bottom wall 156 and a pair
of side walls 158, 160. The tubes 152 each have a pair of
longitudinally spaced end portions 162, 164 and a central portion
166 located between the end portions 162, 164. The end portions
162, 164 of the tubes have a vertical height greater than a height
of the central portion, with a raised shoulder 167 being provided
between the central portion 166 and the end portions 162, 164.
Accordingly, the central portions 166 of adjacent tubes 152 are
spaced apart and the end portions 162, 164 of adjacent tubes 152
are sealed to one another along their top and bottom walls 154,
156.
[0052] The most significant difference between tubes 152 and tubes
12 is that the tubes 152 are not open-ended. Rather, the side walls
158, 160 of tube 152 form part of a continuous perimeter wall which
seals the periphery of tube 152. Further, in all but the uppermost
and lowermost tubes 152, the end portion 162 is provided with
aligned openings 168 extending through both the top and bottom
walls 154, 156 and the opposite end portion 164 is provided with
aligned openings 170 extending through both the top and bottom
walls 154, 156. In FIG. 11, the uppermost tube is labeled 152' and
the lowermost tube is labeled 152''. In the uppermost tube 152',
the end portion 162 is provided with a connection flange 172 which
communicates with the aligned openings 168 and the opposite end
portion 164 is provided with an opening 170 only in its bottom wall
156. There is no opening 170 in the top wall 154; it is either
missing entirely or plugged. Similarly, the end portion 164 of
lowermost tube 152'' is provided with a connection flange 172 and,
although not seen in the drawings, the opposite end portion 162 is
provided with an opening only in its upper wall 154. There is no
opening 168 in the bottom wall 156; it is either missing entirely
or plugged. Therefore, the first fluid, which may preferably
comprise a hot exhaust gas, enters the heat exchanger 150 through
one of the connection flanges 172, flows through the interiors of
the tubes 152 and exits the heat exchanger 150 through the other
connection flange 172. The aligned openings 168 and 170 of tubes
152 provide integrally formed inlet and outlet manifolds and
eliminate the need for end fittings as in the first and second
embodiments.
[0053] Like tubes 12 described above, tubes 152 preferably also
have a rectangular cross section and the top and bottom walls 154,
156 are preferably also provided with protrusions 174 which may be
in the form of truncated conical dimples. It will be appreciated
that the tubes 152 may be provided with protrusions other than, or
in addition to, dimples 174. For example, the tubes 152 could be
provided with spaced, angled ribs provided in their top and/or
bottom walls 154, 156. As shown in FIG. 11, the top wall 154 of
uppermost plate 152' may preferably be free of protrusions 174
since they would serve no purpose in heat exchanger 150. The bottom
wall 156 of lowermost plate 152'' may similarly be free of
protrusions 174.
[0054] Although not shown in FIGS. 10 and 11, the interiors of the
first fluid flow passages may preferably be provided with
corrugated fins which may be identical to fins 80 described
above.
[0055] A plurality of second fluid flow passages 176 are defined by
the spaces between the central portions 166 of adjacent tubes 152.
Each second fluid flow passage 176 has a pair of longitudinally
spaced ends 178 and a pair of transversely spaced sides 180. As
shown in FIG. 11, the second fluid flow passages 176 are sealed at
their ends 178 by the sealed end portions 162, 164 of the adjacent
tubes 152 between which they are formed.
[0056] Heat exchanger 150 further comprises a pair of side plates
182, 184 which seal the sides 180 of the second fluid flow passages
176. Each of the side plates 182, 184 has a pair of
longitudinally-spaced ends 186 and a pair of flanges 188. In the
preferred heat exchanger 150, the side plate 182 is provided with
both the second fluid inlet and outlet openings 190, 192 while the
side plate 184 (of which only one flange is visible in FIG. 10)
does not have an inlet or outlet for the second fluid. It will be
appreciated that the second fluid inlet and outlet openings 190,192
could instead be provided in opposite side plates 182,184 and may
either be offset or directly opposite one another. The second fluid
inlet and outlet openings 190, 192 are also shown in FIGS. 10 and
11 as being provided with inlet and outlet fittings 194, 196
respectively.
[0057] Each side plate 182, 184 is sealed to the side walls 158,
160 of the tubes 152 along one side of the core 11, at least near
its ends. Furthermore, the flanges 188 of each side plate 182, 184
are sealed to an uppermost tube 152 in the stack and to the
lowermost tube 152 in the stack. Therefore, the side plates 182,
184 seal the sides 180 of the second fluid flow passages 176 as in
heat exchanger 120 described above.
[0058] The side plates 182, 184 are preferably U-shaped, with the
flanges 188 being angled relative to the plate side wall 198. The
angle between the edges 188 and the plate side wall is preferably
about 90 degrees. As with plates 44 described above, the flanges
188 of plates 182, 184 preferably frictionally engage the uppermost
and lowermost tubes 152', 152'' during assembly, thereby reducing
or preferably eliminating the need for additional fixturing means
to keep the tubes 152 from shifting their relative positions in the
core prior to brazing. Rather than using side plates 182,184, it
will be appreciated that the heat exchanger 150 could instead be
provided with a housing similar or identical to housing 44
described above.
[0059] As shown in FIG. 11, each of the tubes 152 is preferably
comprised of a pair of plates, an upper plate 200 and a lower plate
202. Upper plate 200 comprises a substantially flat middle portion
204 a continuous peripheral flange 206 and lower plate 202
similarly comprises a middle portion 208 and a continuous
peripheral flange 210. One of the flanges 206, 210 nests within the
other flange as described above with reference to heat exchanger
10.
[0060] FIG. 12 illustrates a heat exchanger 250 according to a
fourth preferred embodiment of the invention. Heat exchanger 250 is
a hybrid of the second and third embodiments in that the tubes 252
of heat exchanger 250 have first end portions. 254 which are
open-ended as in heat exchanger 10 and second end portions 256
which form an integral manifold as in heat exchanger 150. The other
components of heat exchanger 250, namely connecting flange 172,
side plates 182,184 and end fitting 68, are as described above.
[0061] A further preferred feature of the invention is now
described below with reference to FIGS. 13 and 14. FIG. 13 is a
close-up of area C of FIG. 5. In order to provide a seal between
the tubes 12 and the side plates 46,48 of housing 44, it is
necessary to completely fill all the gaps between the tubes 12 and
the side plates 46,48 with filler metal. As shown in FIG. 13, there
is an approximately triangular-shaped gap 100 at the point where
two tubes 12 abut the side plates 46,48 (only side plate 48 is
shown in FIG. 13). If this gap 100 is too large, filler metal will
not reliably be drawn into the gap by capillary flow. In order to
provide more reliable sealing, it may be preferred to modify the
tubes 12 and the side plates 46,48 as shown in FIG. 14 so as to
provide a narrower gap 262 which will be more readily filled.
Firstly, according to the modified structure of FIG. 14, the shapes
of the plates 88,90 making up tubes 12 are somewhat modified to
have slightly more rounded edges 264,266 and the height of the side
portions 94 of lower plates 90 are somewhat reduced. Secondly, the
side plates 46,48 (only plate 48 is visible in the close-up of FIG.
14) are formed with ribs 268, at least near the ends of the side
plates 46,48. These ribs 268 extend into the area between adjacent
tubes 12 so as to provide a relatively narrow gap 262.
[0062] FIG. 15 illustrates a pair of plates 88' and 90' of a heat
exchanger according to a sixth preferred embodiment of the
invention. Plates 88' and 90' together define a heat exchanger tube
12' which is substantially identical to tubes 12 of heat exchanger
10 described above except that the upper surface 14' of tube 12' is
provided with an elongate, upstanding rib 270 extending
longitudinally from one end portion 22' and along the central
portion 26' of tube 12'. The rib 270 has a height which is
substantially the same as that of the end portion 22' and has one
end 272 which preferably forms a smooth transition with the end
portion 22' of tube 12'. The other end 274 of rib 270 is spaced
from the other end portion 24' of tube 12'. Similarly, the lower
surface 16' of tube 12' is provided with an elongate, depressed rib
276 extending longitudinally from end portion 22'. The rib 276 has
a height which is substantially the same as that of end portion
22', has one end 278 which preferably forms a smooth transition
with the end portion 22' of tube 12' and an opposite end 280 spaced
from the other end portion 22'. The same effect will be produced by
providing only one of the upper surface 14' or the lower surface
16' of tube 12' with a rib which has a height equal to the height
of the second fluid flow passage 38 between adjacent tubes 12'.
[0063] When a core 11' (not shown) is formed by stacking tubes 12',
the ribs 270, 276 of adjacent tubes 12' engage one another, thereby
forming a barrier against transverse flow of the second fluid
directly across the core. Rather, the second fluid must flow around
the flow barrier formed by ribs 270, 276 and pass through a gap
between the ends 274, 280 of ribs 270, 276 and the end portions 24'
of the adjacent tubes 12'. In this embodiment, it may be
advantageous to locate the second fluid inlet and outlet openings
(not shown) of the side plates (not shown) directly across the core
11' from one another, and adjacent the ends 22' of tubes 12', so as
to maximize the length of the flow path followed by the second heat
exchange fluid. The flow between an inlet and outlet situated in
these positions is indicated by the arrows in FIG. 15. It will be
appreciated that ribs may instead be provided in the tube interiors
to lengthen the flow path of the first fluid in a similar
manner.
[0064] A heat exchanger 300 according to a seventh preferred
embodiment of the invention is now described below with reference
to FIGS. 16 and 17. Heat exchanger 300 includes a core 11 and a
pair of end fittings 68 which are shown as being identical to those
of heat exchangers 10 and 120 described above. Heat exchanger 300
further comprises a pair of side plates 122', 124' which are
similar to side plates 122, 124 of heat exchanger 120 and are
therefore described using like reference numerals.
[0065] The side plates 122', 124' seal the sides of the second
fluid flow passages 38. Side plate 122' is provided with an inlet
opening 126' and a raised inlet manifold 128' and side plate 124'
is provided with an outlet opening 130' and a raised outlet
manifold 132'.
[0066] Heat exchanger 300 further comprises a pair of end plates
302, 304 which, in the preferred embodiment of FIGS. 16 and 17, are
flat and rectangular. The end plates are of a length sufficient to
overlap with and sealingly engage the end portions 22, 24 of the
uppermost and lowermost tubes 12 of the core 11. The end plates
302, 304 preferably are of substantially the same width as the core
11. Therefore, additional second fluid flow passages are formed
between the end plates 302, 304 and the core 11, in an identical
manner as described above with reference to the end plates 50, 52
of heat exchanger 10.
[0067] Each side plate 122', 124' overlaps and is sealed to sides
of the core 11 in the manner described above with reference to heat
exchanger 150. The side plates 122',124' are preferably U-shaped,
having angled flanges which are sealed to the end plates 302, 304,
thereby sealing the sides of the second fluid flow passages 38. The
flanges preferably extend the full length of the end plates 302,
304. As shown in FIGS. 16 and 17, side plate 122' is provided with
flanges 134', 136' and side plate 124' is provided with flanges
138', 140'. One flange 134' of plate 122' is sealed to the upper
end plate 302 the other flange 136' is sealed to the lower end
plate 304. Similarly, the flanges 138',140' of the other plate 124'
are sealed to the upper and lower end plates 302, 304,
respectively.
[0068] Preferably, during assembly of the heat exchanger 300, the
angled flanges 134', 136', 138', 140' of plates 122',124'
frictionally engage the end plates 302, 304, thereby reducing or
eliminating the need for additional fixturing means to keep the end
plates 302, 304 and the tubes 12 of core 11 from shifting their
relative positions prior to being joined, for example by brazing.
Accordingly, the side plates 122',124' provide "self-fixturing"
during assembly of the heat exchanger and simplify the
manufacturing process.
[0069] The heat exchanger 300 is shown in its assembled state in
FIG. 17. As shown, the flanges 70 of end fittings 68 may preferably
be spaced from the side plates 122', 124' and the end plates 302,
304 in the manner described above with reference to FIG. 4A.
Alternatively, the end plates 302, 304 may be overlapped by the
fittings 68 in the manner shown in FIG. 4B, in which case it may be
preferred to use side plates 122, 124 identical to those of heat
exchanger 150 in which the flanges 134, 136, 138, 140 which
terminate short of the ends of the plates 122, 124 such that the
flanges are not overlapped by the fittings 68. Alternatively, the
end plates 302, 304 may overlap the fittings 68 in the manner shown
in FIG. 4C.
[0070] Although the invention has been described in connection with
certain preferred embodiments, it is not limited thereto. Rather,
the invention includes within its scope all embodiments which may
fall within the scope of the following claims.
* * * * *